Eskom power stations tripped 711 times in a single year - causing a surge in fuel costs

Eskom's used more fuel oil due to increasing trips and unplanned outages.
Eskom's used more fuel oil due to increasing trips and unplanned outages.
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  • Eskom used 130% more fuel oil than anticipated for coal-fired power stations during the 2020 financial year.
  • Every time a coal-fired power station tripped, fuel has to be used to start it up again.
  • Power stations tripped 711 times over the past year - 72% more than in the previous year. 

Eskom used 130% more fuel oil than anticipated for coal-fired power stations during the 2020 financial year.

According to its Regulatory Clearing Account (RCA) Year 1 application to the National Energy Regulator of South Africa (Nersa), submitted on 11 December 2020, Eskom's start-up fuel oil costs account for about a quarter of the R8.4 billion it seeks to claw back.

The RCA application is a mechanism Eskom uses to retrospectively adjust for an over or under-recovery in revenue for a particular year, due to actual events differing from assumptions made by Nersa when granting a tariff. In this application, Eskom is seeking to recover revenue due to sales volumes determined by Nersa which did not materialise. A decision by the regulator is due in August, Fin24 previously reported.

The application also accounts for variances in assumptions made of primary energy costs. The major driver of primary energy costs was breakdowns at its power stations. 

Heavy fuel oil is used to start up and shutdown coal fired power stations. The number of starts required depends on the number of outages - either planned or unplanned - and the number of trips at the units of a station, Eskom explained.

Start-up fuel-oil contributed R2.2 billion to the RCA, the application showed.

"The number of unplanned outages and trips were significantly higher in the FY2020 than what was anticipated at the time of the 2020 application and determination. Hence the use of fuel oil increased significantly as well," the application read.

The allowable litres for the financial year 2020 application was 227 million litres, but Eskom ended up using 525 million litres. Eskom highlighted that the cost of fuel is also driven by the US dollar price - beyond the utility's control. "The price of oil and the rand-dollar exchange rate [are] very volatile and difficult to predict into the future with accuracy," the application read.

Eskom also indicated that in financial year 2019, its generation fleet tripped 414 times. This increased by 72% to 711 the next year.

Another contributor to the RCA is the use of Open Cycle Gas Turbines (OCGT). According to Eskom, the R2.4 billion cost recovery should be allowed as it was incurred to ensure security of supply. The OCGT is deployed as a last resort before load shedding. Open-cycle gas turbines run on diesel and  is a very expensive way to generate power.

The actual use of OCGTs was significantly higher than assumed for the financial year 2020 revenue application and Nersa's decision.

"This higher usage was essential to avoid, and in some cases limit load shedding in the second half of the year which was primarily as a result of the lower plant availability."

In the application Eskom pointed out that the root cause of the generation fleet's poor performance is due to delays in investment decisions to build new generation capacity in the late 1990s to meet demand in 2007. When the decision was eventually made to build additional capacity in 2006, it was already too late.

Problems were exacerbated by the delays in construction of coal-fired stations Medupi and Kusile. Deferred maintenance in order to meet electricity demand, especially with the lead up to the 2010 FIFA World Cup, also had a negative impact to the health of stations.

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